1. Field of the Invention
This invention relates to a preserving system for cryopreserving biological preservation specimens such as frozen cells, tissue cells, sperms, ova for a long term.
2. Detailed Description of the Prior Art
A preserving system using liquid nitrogen (LN2) has ever been disclosed by the Japanese Patent Laid-Open No. 1998-243951.
In the preserving system described in the Japanese Patent Publication, preservation specimens (for example, the biological specimens) were cryopreserved in a liquid nitrogen cylinder by soaking them therein.
When liquid nitrogen is used, it vaporizes at −189° C. so the temperature can be lowered close to −189° C. As a result, the biological specimens and so on can be cryopreserved for a long time.
Moreover, a preserving system of the same kind as the above is known, which is provided with a preserving vessel to be supplied with liquid nitrogen and a cylinder for supplying the liquid nitrogen to this preserving vessel. As for the preserving system, such a system as the liquid nitrogen in the preserving vessel vaporizes is also known, automatically fed when it decreases to a predetermined quantity or below by vaporizing.
In the preserving system, the cryopreservation temperature is maintained by the latent heat of vaporization of the liquid nitrogen and thus the vaporized nitrogen is left as it is without being collected, therefore, the drawbacks of the system is a large consumption of liquid nitrogen and a high economical burden.
Moreover, as described above, in the system arranged so as to be automatically replenished with a vaporized amount from the liquid nitrogen cylinder, the cylinder has to be regularly replenished with liquid nitrogen, and once the replenishment is neglected, the temperature of the specimens preserved in the preserving vessel rises, and in a worst case, the specimens become extinct. Therefore, the replenishment of liquid nitrogen has been a large troublesome job (a drawback) for a custodian.
Therefore, it has been desired to compensate for the above-mentioned two drawbacks and develop a preserving system capable of securing the safety of specimens to be preserved.